186 



FISHEKY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Migrations and wanderings. — It has long been 

 known that cod carry out extensive migrations 

 in some regions, but that they are more nearly 

 stationary in others. European (especially the 

 Scandinavian) biologists have succeeded in tracing 

 the major outlines of their movements for North 

 European seas, and enough evidence has accumu- 

 lated to show that their travels fall into the same 

 categories in the one side of the Atlantic as in 

 the other. These categories are: (a) involuntary 

 drifts by the eggs and by the larvae before they 

 take to the bottom; (b) the various journeyings 

 by the older cod in search of food; (c) journeys 

 associated with the concentrations of cod on 

 particular spawning grounds; and (d) regular 

 seasonal migrations (with return movement) 

 between different regions that are suitable for 

 cod during different parts of the year. 



To begin with, the eggs, larvae, and young fry 

 of the cod, bike those of so many other sea fishes, 

 drift helplessly with the current from the time 

 they are spawned until they seek the bottom (a 

 fact established by European observations too 

 numerous to list). 72 The length of this period 

 (varying in duration in different seas) depends 

 partly on whether the fry are near land or are 

 far out at sea, and partly on whether they are 

 floating over deep water or over shoal. It is not 

 likely to last for more than two months for fish 

 that are hatched on the inshore spawning grounds 

 in the Gulf of Maine, where the bottom is within 

 easy reach. Even so, it is extremely unlikely 

 that any cod fry take to the bottom near where 

 they were spawned. 



This matter is discussed further in relation to 

 the occurrence of the cod in our Gulf (p. 190). 



The journeyings of the cod that are associated 

 with their spawning are especially extensive along 

 the Norwegian coast, where they have been the 

 subject of much study, leading (among other 

 things) to the very interesting probability that 

 their journeys up and down the coast of Norway 

 are chiefly involuntary, for the ripe fish drifting 

 north become so fat that they tend to be suspended 

 in the water near the surface, whereas the spent 

 fish become so thin that they are deeper 

 down in the water. 73 But there is no reason to 



" In European seas young cod often live under the disks of the large red 

 Jellyfish (Ci/anca), but they have not yet been found In this situation in the 

 Gulf of Maine. 



" See especially HJort, Journal du Consel], Cons. Perm. Interaat. Eiplor. 

 Mer, vol. 1, No. 1, 1926, p. 9. 



suppose that any of our Gulf of Maine cod need 

 travel far to reach the localities where they spawn. 



In the extreme northern and southern fringes of 

 their geographic range cod are regularly "migra- 

 tory" in the common understanding of the term. 

 Thus it is only in summer and early autumn that 

 they visit the waters of the polar current along 

 the eastern coast of Labrador, from which they 

 withdraw again later in the autumn, to pass the 

 winter and spring either to the southward or in 

 deep water. On the other hand, it is only during 

 autumn, winter, and early spring that cod are 

 caught off the coasts of southern New England, 

 of New York, of New Jersey, or further south. 



The fish that winter along this westerly and 

 southerly extension of the cod's geographic range 

 appear off southern Massachusetts in mid-October; 

 off western Long Island and off the coast of New 

 Jersey in November; they go back eastward again 

 by the first part of May. And the numbers involved 

 are large enough to support a profitable autumn- 

 winter and early spring fishery from Nantucket 

 to New Jersey. 



Tagging experiments carried out by the U. S. 

 Bureau of Fisheries, first at Woods Hole in the 

 winters of 1898-1 90 1, 74 and in various parts of our 

 Gulf on a much larger scale from 1923-1930, 76 have 

 shown that most of the fish that take part in this 

 westerly movement pass the summers in the 

 Nantucket Shoals region. But it is clear that a 

 large part of the cod stock that summers on the 

 Shoals fails to join this westerly mass movement in 

 autumn, for fish tagged there in summer have been 

 recaptured there the next winter, while many 

 others have been recaught there the following 

 spring. And it is established now that the great 

 majority of the cod that live off our coasts from 

 Cape Cod to northern Nova Scotia, in the south- 

 ern part of the Gulf of St. Lawrence, and on the 

 southern part of the Grand Banks, can fairly be 

 termed "nonmigratory" in a broad sense. 



Breeding habits. — The cod is one of the more 

 prolific fishes. A female 39 or 40 inches long may 

 be expected to produce about 3,000,000 eggs 

 yearly, one of 41 inches at least 4,000,000. And 

 Earll estimated the number in a 52%-inch fish 

 weighing 51 pounds at 8,989,094, with 9,100,000 in 



" Smith, Rept. U. S. Comm. Fish (1901) 1902, pp. 193-208. 



" 22,884 fish tagged in the rogion of Nantucket Shoals, and about 30,000 in 

 other parts of the Gulf of Maine, Including the offshore Banks, 308 fish 

 recaptured westward from Marthas Vineyard,. For further details, see 

 Schroeder (Bull. TJ. 8. Bureau of Fisheries, vol. 48, 1930, pp. 1-136). 



